摘要:

The problem of electromagnetic wave propagation in the linearly accelerated dielectric medium is studied by using the extended Maxwell‐Minkowski theory. First, from the viewpoint of the extended Maxwell‐Minkowski theory, the well‐known problem of reflection and transmission of electromagnetic waves by the moving dielectric with constant velocity is studied by using the Galilean transformations instead of the Lorentz transformations. It is shown that the problem can be solved and the same results can be obtained as those obtained by using the Lorentz transformations. Then, with the aid of the covariant properties of Maxwell’s equations, a rigorous solution of the electromagnetic wave in a linearly accelerated dielectric is founded. The phenomena of bending of light rays in the accelerated system and the relativistic energy velocity and phase velocity addition law for the accelerated motion are derived from the rigorous solution obtained. The problem of reflection and transmission of the electromagnetic wave at normal incidence by a linearly accelerated dielectric interface is solved using the solution obtained. The reflected wave and the transmitted wave are obtained, and their interesting properties concerning the Doppler effect and drag effect are discussed in comparison with the case of constant‐velocity motion.

ISSN:0021-8979    

DOI:10.1063/1.325483

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new technique is developed to determine the dispersion relation and the propagational speeds of waves in dispersive solids. The phase spectrum of a broadband pulse is linearly related to the dispersion relation of the dispersive medium. The method is simpler than the continuous‐wave phase comparison technique. Application is made to measure the phase and group velocities of waves in fiber‐reinforced composite materials and in thin wires. This technique is expected to be applicable to measurements of acoustic or electromagnetic wave speeds in other dispersive media.

ISSN:0021-8979    

DOI:10.1063/1.325484

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A calibrated two‐color temperature method has been developed for the measurement of time‐dependent temperatures in low‐pressure gases following laser excitation. Ratios of ir fluorescence signals arising from specific vibrational manifolds are used to determine the magnitude of laser heating, the vibrational temperatures of individual modes, and density fluctuations due to gasdynamic expansion following spatially inhomogeneous excitation. This technique has been applied to a prototype system consisting of SF6, SO2, and CH3F exposed to TEA CO2laser excitation of the &ngr;3mode of SF6. Prior toV‐T/Rrelaxation, this system cannot be described by a single vibrational temperature.

ISSN:0021-8979    

DOI:10.1063/1.325485

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A solution &fgr; (r,z) is given of a rotationally symmetric boundary‐value problem: &fgr; (A,z) =0 forz⩽0 andz⩾L, and &fgr; (A,z) =F(z) for 0⩾z⩾L.AandLare given constants andF(z) is a given function which is symmetrical with respect to the planez=L/2. The solution is in the form of an infinite Fourier‐Bessel series, the coefficients of which can be found without inverting matrices. It is shown that the given field can be approximated physically by means of two long equipotential cylinders and one or more central electrodes of curved cross sections. Since the electric intensity is also known at all points, the solution allows a precise determination of the electron‐optical properties of a wide variety of electrostatic Einzel lenses with curved electrodes.

ISSN:0021-8979    

DOI:10.1063/1.325486

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

In the emission or absorption of electromagnetic radiation by small objects, generally speaking, the smaller the size‐wavelength ratio and the higher the modal number, the larger will be the ratio of reactive to real power flow. However, if the source is internally lossless and free of constraints, charge‐current relationships may exist which produce combinatory sets of multipolar electric and magnetic moments for any modal number which yields zero net reactive power flow—a resonant condition. The needed reactive energy for resonance to occur decreases with increasing modal number. The radiativeQis very large and will give rise to reactive forces that are quite capable of driving an atomic source to radiate energy h&slash;&ohgr; during electronic transition times. When resonance occurs, the resulting radiation has an energy–to–angular‐momentum ratiom&ohgr;, wheremis an integer, and a combinatory set of modal coefficients exists for which the radiation is largely directed in that the ratio of exchanged momentum to exchanged energy is greater than 0.8/c. Other mechanisms may supply the momentum increment needed to make the exchanged ratio be exactly 1/c. This continuum‐field description appears to be adequate to describe the radiative portion of atomic electronic transitions, treated as a boundary‐value problem.

ISSN:0021-8979    

DOI:10.1063/1.325487

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper presents an investigation of nonlinear third‐harmonic generation in a weakly collisional magnetoplasma due to simultaneous propagation of both the right and left circularly polarized modes, having a Gaussian intensity distribution; self‐focusing has been taken into account. At moderate powers, the self‐focusing is seen to enhance the harmonic output by two orders of magnitude; at high powers, propagation occurs in an almost uniform waveguide devoid of plasma, and the harmonic output is, consequently, decreased. In the vicinity (&ohgr;c/&ohgr;=0.7) of the electron cyclotron resonance, the harmonic output of the extraordinary mode is enhanced by an order of magnitude; the present theory is not applicable at resonance.

ISSN:0021-8979    

DOI:10.1063/1.325488

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A model of the coupling of a Lambertian LED and a spherical‐ended fiber is proposed and analyzed by means of geometrical optics. The system of this optical coupling can be regarded as a simple optical system which consists of a light source, a principal plane, and an aperture stop. The model analyzed is that in which a light source and an aperture stop are on the anterior and the posterior focal planes, respectively. The maximum incident angle &fgr;minto the fiber is determined from the condition that the ray passing through the anterior focal point is not obstructed by the aperture stop, which has the same diameter as the core one. According to the theoretical analysis, the coupling efficiency for the Lambertian LED and the spherical‐ended fiber is sin2&fgr;mprovided thatd0?dcand (dc/d0)2 sin2&fgr;mprovided thatd0≳dc, whered0is the emitting diameter anddcis the critical diameter defined by the critical angle &fgr;cof the light propagation in the fiber. For two kinds of LED’s with emitting diameters of 35 and 85 &mgr;m, the coupling experiment was performed on spherical‐ended fibers which had a numerical aperture NA of 0.14 and a core diameter of 85 &mgr;m. The spherical ends of fibers were fabricated to radiirfrom 75 to 170 &mgr;m. A good agreement between the theoretical and experimental results is obtained. In the case that the emitting diameter is 35 &mgr;m and the spherical radius is 75 &mgr;m, the calculated efficiciency is 6.3&percent;, three times greater than that for a flat‐ended fiber. It is shown that the coupling efficiency can be improved by using the spherical‐ended fiber with the spherical radius less than aboutd1/(4NA), whered1is the core diameter. It is also shown that the maximum coupling efficiency for the LED with the emitting diameter ofd0is obtained by the fiber with the spherical radius less than aboutd0/(4NA).

ISSN:0021-8979    

DOI:10.1063/1.325489

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A copper‐vapor laser utilizing copper acetylacetonate as a copper atom donor in a flowing gas heated discharge tube has been studied. As in the other metal‐vapor laser systems based upon the dissociation of a metal salt, two successive discharges are required to achieve laser action. The output energy of such a system would appear to be comparable to that obtained in the CuCl systems; however, the operating temperature is much lower.

ISSN:0021-8979    

DOI:10.1063/1.325490

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The generation of surface acoustic waves by interdigital transducers in materials with high and strain‐dependent dielectric constants, which are not necessarily piezoelectric, was studied theoretically using Lamb’s integral‐solution method and the flat‐field approximation of Tseng for the solutions of the wave equation. The influence of the dependence of the dielectric constant on the strain was considered in the approximation given by Pekar and Ogg. As a result, a transducer gain proportional to an applied dc field has been obtained. With respect to the frequency responses, an increased output at higher odd harmonics as compared to transducers on piezoelectric crystals was found. The transducers are shown to be tunable because of a stiffening of the surface‐wave velocity by the applied field. Thus, amplitude modulation and frequency modulation should be possible in a simple manner.

ISSN:0021-8979    

DOI:10.1063/1.325476

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Steady periodic temperature, transient temperature, and stresses produced in an isotropic cylindrical conductor carrying an electric alternating current are calculated. The investigations are made for the small skin effect when the current density is homogeneous.

ISSN:0021-8979    

DOI:10.1063/1.325477

出版商:AIP    

年代:1978

数据来源: AIP